1. Field of the Invention
This invention pertains generally to the field of vehicle display units that present navigation information to the user of a vehicle such as the pilot of an aircraft.
2. Description of the Related Art
Aircraft fly in all sorts of weather conditions that can be generally categorized as flight under Visual Meteorological Conditions (“VMC”) or Instrument Meteorological Conditions (“IMC”). When operating in VMC or IMC weather conditions, flight may be conducted under Visual Flight Rules (“VFR”) or Instrument Flight Rules (“IFR”), respectively. Generally, flight under VFR occurs when a pilot can fly with reference to visual cues located outside the aircraft; when the pilot cannot rely on outside visual cues, e.g., when there is poor visibility, he or she conducts the flight in IMC under IFR.
To assist the pilot when landing on a runway at an airport when flying in IMC, a pilot may perform an instrument approach procedure (“IAP”). The IAP may be categorized as a precision approach procedure or a non-precision approach procedure, each designed with a final approach fix (“FAF”) and a missed approach point (“MAP”). The MAP may be considered as a point along the IAP at which time the pilot decides to land the aircraft or execute a missed approach procedure, where such decision may depend upon the pilot's ability to see the runway environment.
The MAP may vary and depend upon the approach procedure being flown. For a precision approach procedure, the MAP may be located at a point along a glide slope at which decision height (“DH”) or decision altitude (“DA”) is reached. In one type of non-precision approach procedure, the pilot may determine the MAP with a navigational fix or navigational aid (“NAVAID”) where the NAVAID facility upon which the IAP is based is located on the airport. In another type of non-precision approach procedure, the MAP may be determined with defined waypoints used in conjunction with a global positioning system (“GPS”) or VOR/DME RNAV (which is defined as very high frequency omnidirectional range/distance measuring equipment area navigation).
In another type of non-precision approach procedure where the NAVAID upon which the IAP is based is located away from the airport, the MAP may be determined by timing the IAP when passing the FAF; when performing this type non-precision approach procedure, it is not uncommon for a pilot to forget to time the approach when passing the FAF. Without a timer, the pilot may not know when he or she arrives at the MAP at the correct time when a decision needs to be made. This could lead to a loss of a pilot's situational awareness and increase the risk of experiencing a tragic consequence where, for instance, the aircraft is operating in or near an area of mountainous terrain.